Solution to:
Acquiring Animals

The first statement says:

A horse is worth as much as two bulls and one sheep.

According to the second statement, a bull is worth as much as two cows,
from which follows that two bulls are worth as much as four cows.
In the first statement, the part "two bulls" therefore can be replaced by "four cows":

A horse is worth as much as four cows and one sheep.

According to the third statement, two cows are worth as much as five donkeys,
so we can replace "four cows" by "ten donkeys":

A horse is worth as much as ten donkeys and one sheep.

According to the fourth statement, a donkey is worth as much as four sheep,
so we can replace "ten donkeys" by "forty sheep":